Blending and doubling of the raw staple fiber stock is a primary operation in the textile industry and has been accomplished in a variety of ways. Not only is it necessary to blend and double fibers of like kind from different bales, but it has become more and more important to blend and double unlike fibers into blends with specified percentages of different fibers mixed and blended uniformly and homogeneously, and with the proportions of the different fibers held substantially constant.
The fibers are normally fed from the bales either manually or mechanically in small portions taken in sequence from many bales and deposited on the aprons of automatic hopper feeders which open, even, mix, and feed the fibers to further processing equipment. A number of such feeders disposed in a line and arranged to feed onto a horizontal conveyor is a common practice for creating blends. Each of the feeders may have a different type of fiber fed thereto and is usually equipped with a weigh pan or other measuring device which collects a predetermined weight of fibers in tufts from the feeder and holds the fibers until the weigh pans of all of the feeders have collected therein predetermined weights, or loads, of fibers. At that time, all weigh pans dump simultaneously on the conveyor, where repeated synchronized dumps form layered "sandwiches" containing suitable proportions of each different fiber for presentation to the action of a beater blender for simultaneous separation or homogenization of fibers from all layers as the sandwich is gradually fed into the beater. Various patterns or arrays of weigh pan dumps onto the conveyor have been accomplished by predetermined synchronizations of the conveyor and the weigh pans. U.S. Pat. Nos. 3,071,202, 3,080,617, and 3,439,838 disclose typical blending apparatus and methods of the aforementioned types.
U.S. Pat. No. 3,071,202 discloses a plurality of continuously running distribution conveyors which receive weigh pan loads of fibers simultaneously from a line of spaced feeders, and a collecting conveyor beneath the distribution conveyors which collects the weigh pan loads from the distribution conveyors at a rate which spreads each weigh pan load upon the collecting conveyor to form a continuous layer of fibers from each feeder and accompanying distribution conveyor on the collecting conveyor. This forms a continuous sandwich of fiber layers on the collecting conveyor, which, when fed into a beater blender, results in uniform blending of the various fibers.
A modification disclosed in the above patent eliminates the distributing conveyors and dumps the weigh pan loads directly on the collecting conveyor. However, the collecting conveyor speed must be synchronized with the weigh pan dumps so that individual "sandwiches" or stacks of layers of the different weigh pan loads are formed on the collecting conveyor and simultaneously fed into a beater blender for the intimate blending of the various fibers as desired.
U.S. Pat. No. 3,080,617 is apparently aimed toward eliminating a problem which occurs with apparatus of the type of the previously discussed U.S. Pat. No. 3,071,202. This problem consists of the typical tendency of the dumped weigh pan loads of fibers to fall onto the collecting conveyor in bunched widthwise form which does not provide even layers for the sandwich. While the different weigh pan loads may be distributed uniformly lengthwise of the collecting conveyor, the distribution across the width of the collecting conveyor is likely to be in streaks or essentially in somewhat haphazard widthwise layers rather than horizontal layers. Fibers fed from the collecting conveyor into a beater blender in this condition may result in unsatisfactory blending by the beater blender, and this patent discloses means for further mixing of these side-by-side variations of fiber content by running the partially blended fibers from the beater blender through a transversely baffled mixing chamber which re-distributes the side-wise variations of fiber blend more uniformly before conveying these further mixed fibers on a lateral conveyor to a card-like fiber processing machine for further opening, mixing, and blending. Such an arrangement requires more complicated apparatus and additional floor space.
U.S. Pat. No. 3,439,838 discloses a variation of the above-mentioned U.S. Pat. No. 3,071,202 for achieving improved blending results. This variation includes running the collecting conveyor at a sufficiently slow apeed such that successive weigh pan loads from each feeder overlap each other, whereby a continuous sandwich of fiber loads formed on the collector conveyor will contain more layers than feeders. A generally similar blending process is utilized in blending equipment manufactured by James Hunter Machine Co., Mauldin, S.C. However, even with this arrangement there may still be a non-uniformity of layers transversely of the collecting conveyor as mentioned in the preceding paragraph, and, also, the sandwich may be thicker and therefore more difficult for the beater to blend properly.
In the fiber blending apparatus of the present invention, means is provided for forming effectively continuous sandwiches of weigh pan loads of fibers which are fed to a beater blender, and the layers are substantially uniform in thickness and in weight over their entire extent, so that when processed through the beater blender, the resulting blend will have a maximum homogeneity. This improved apparatus requires a minimum of extra floor space, no complicated synchronization of collecting conveyor and feeders, and the beater blender by itself provides a highly satisfactory degree of blending without resort to an extra stage of mechanical working of the fibers.